re: Cat 5, outside plant, commercial grade video over t.p., and Ethernet
Ray, this may be a little off topic to the discussion at hand. I posted the following message, almost identically, on the Gilder thread [post # 2263] in response to some earlier questions you had, earlier. I'm posting it here in FCTF to keep within the scope of DH's original intent of this thread.
I don't know if I've answered or even addressed your original qeustion adequately, and if i've not, then fire away.
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If I could suggest, let's put Tut and other plays in the DSL space aside for the moment and discuss some generics here.
DSL was originally designed around the longitudinal parameters associated with outside
plant (OSP) non-loaded twisted pairs. Reference to Cat 5 cable is often confused with
this, when making reference to high quality OSP.
Cat 5, by definition, is an in-building LAN cabling specification with specific
transmission- and environmental-related performance stipulations and distance
constraints (limited to 90 meters on the floor, and 10 meters in closets and under
desks). It was brought about by many years of grief and tears in the commercial
building cabling space.
This taxonomy of in building cabling, where different grades of 4-pair cables are rated
as Cat 3, 4 and 5, was defined by the Telecommunications Industry Association and
ANSI in the ANSI/EIA/TIA/ 568 Standard about eight or nine years ago, and has undergone constant refinement with increasing demands made in the areas of speed and ingress (total x-talk, noise, emi/rfi etc.) tolerances.
Their 570 standard defines the smaller commercial and residential models. Standard
569 defines pathways and spaces in commercial structures, and is primarily an aid to
architects and facilities managers in prep'ing base-building and work areas for the laying
of cables. These and other standards are listed below.
From: cableu.net
--begin snip
EIA/TIA 568A Commercial Building Telecommunications Wiring Standard
EIA/TIA 569A Telecommunications Wiring Pathways and Spaces
EIA/TIA 570 Light Commercial and Residential Telecommunications Cabling
EIA/TIA 606 Telecommunications Cabling System Administration
EIA/TIA 607 Telecommunications System Grounding and Bonding Requirements
Several technical service bulletins (TSBs) have also been published
relating to this standard, to clarify various points in the standard:
TSB-36 UTP Categories 3, 4, and 5 Defined
TSB 40A UTP Connecting hardware for Category 3, 4, 5
TSB-53 Additional specifications for STP (shielded twisted pair) hardware
TSB-67 Transmission performance specification for field testing UTP
TIA/TSB-72: Centralized Optical Fiber Cabling Guidelines
TSB-75 Defines "zone distribution systems" for horizontal wiring
-----end snip
As to who "owns" Ethernet, I don't know this to be pertinent anymore, maybe it still is,
but at one time all 802.3 MAC Layer addresses for Ethernet were administered and
parceled out by DEC, Xerox and IBM. They each maintained IEEE allocations of
addresses in a custodial manner, and were designated by the IEEE (I think?), since
Ethernet is an IEEE standard primarily, to dole them out to other manufacturers to burn
into their NIC cards, as required. I am not privy to the deal making end of this,
however.
And the data link attributes of Ethernet, which are in fact situated at Layer 2, converge
with physical media ~half way down Layer One of the OSI RM, as Peter indicated.
However, since Ethernet Layer 2 data link control attributes do exist, I would have to
differ with Peter on this one, a bit, but I'll give him the benefit of simply omitting it in his
focus on the lower vs higher layer uses of Ethernet, and simply didn't include L2 in the
post.
But there are no layer 3 and 4 processes taking place in Ethernet.
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As for hotel rooms, Cat 5 twisted pair has now begun to displace coax in the video
space, read: TV and entertainment links in hotels, hospital bedsides, in-homes. Many
new installations borrow from bal/un technologies such as those which were pioneered
by T back in the late Eighties/early Nineties, and later perfected by a British company
called CCC, a while back. Now there are a number of such video/tp companies out
there, and they are beginning to penetrate, broadly.
In one example here, we are talking about two paths, which could be defined either or
both, physically or logically, depending on a number of application and environmental
variables. Let's consider two separate physical Cat x cabling paths, where x equals the
recommended grade by the manufacturer.
Often, Cat 5 will be used, anyway, but in ways which violate 100 meter distance rules in the risers. But that's okay because the video bal/uns do not abide by those constraints the way NIC manufacturers do.
One path would be used for sending actual video content over a plain old bal/un (an impedance matching device between coax and tp) from a controller in the control room to the guest's or patient's room --in commercial enterprise applications this is already estalished in video conferencing rooms and conference areas, and to many desktops-- where another bal/un exists prior to plugging into the TV, and a second cable (or arguably a second pair in the same cable, since there are four pairs per Cat x cables) for session control and other LAN-related purposes. In business, this often means support of collaborative applications and side chat, as well.
Some variants of this employ a single pair and resort to subcarrier techniques instead,
for the TCP/IP over Ethernet parts.
Regards, Frank Coluccio |
